Double hand with a through hole

ABSTRACT

A double hand applicable to an industrial robot comprises two hand units (2, 3) comprising at least two pairs, one each, of fingers (2-1 and 2-2, 3-1 and 3-2) and plate members (2-3, 3-3) of a pressing unit (4) disposed in parallel along the center axis of the fingers. The hand units (2, 3) are connected through a pressing mechanism (4) to constitute a double hand in a manner that the respective gripping center axis of the two hand units are in alignment, the respective plate members (2-3, 3-3) of the pressing unit are disposed opposite to each other and the opening sides of the respective pairs of fingers of the two hand units are directed in opposite directions to each other. An opening (6) for allowing a workpiece to penetrate through the plate members is provided for each of the plate members (2-3, 3-3) of the pressing unit attached to the hand units (2, 3 ) respectively coaxially with the gripping center axis so that both hand units (2, 3) are allowed to move freely relative to the workpiece gripped by the hand units (2, 3) along the gripping center axis.

DESCRIPTION

1. Field of the Invention

This invention relates to an industrial robot employed for loading andunloading a workpiece to a machine tool, more particularly to animproved workpiece-gripping double hand of an industrial robot.

2. Background Art

In loading a workpiece on the chuck of a machine tool, for example, alathe, and unloading the machined workpiece from the chuck by the use ofan industrial robot, a double hand, in general, is used in order toreduce the loading and unloading time.

A double hand comprises two parallely disposed hand units ofapproximately analogous construction connected by a pressing mechanism.The plate members of the pressing mechanism are interposed between thefingers of one hand unit and the fingers of the other hand unit.

In machining a workpiece on a lathe or another machine tool, it is oftennecessary to machine one end of the workpiece first, and then to chuckthe workpiece again at the machined end to machine the other end. Insuch a machining procedure, a conventional double hand is inverted afterunloading a machined workpiece and placing the same on a table and thengrip the workpiece again. This conventional procedure is disadvantageoussince changing the grip requires a long time.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to eliminate this disadvantageof conventional double hands and to provide a double hand of aconstruction capable of performing the change of grip easily and in ashort time. According to the present invention, the object of theinvention is attained by providing an opening for the plate member ofeach hand unit of a double hand with the center of the opening beingcoincident with the center axis of workpiece gripping.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of an industrial robot to which the doublehand of the present invention is preferably applied;

FIG. 2 is a side elevation of a double hand of the present invention;

FIG. 3 is a top plan view of the double hand of FIG. 2;

FIG. 4 is a side elevation of a plate member of the pressing unit;

FIG. 5 is a sectional view of the pressing mechanism; and

FIG. 6 is a side elevation of the driving mechanism of the hand unit.

BEST MODE OF CARRYING OUT THE INVENTION

Referring to FIG. 1 illustrating, in a perspective view, an industrialrobot to which a double hand of the present invention is suitablyapplicable, the arm of the industrial robot is adapted to be controlledby a servomechanism so as to perform a horizontal linear motion alongthe X-axis, swiveling motion in a vertical plane along the course Abetween the horizontal position and the vertical position, twistingmotion in a vertical plane from the vertical position along the courseB, vertical linear motion along the Z-axis, and swiveling motion in ahorizontal plane along the course C. The turning motion of the wristpart about the α-axis can selectively be controlled between 0°/90° and0°/180° turning positions by means of ON/OFF control.

FIGS. 2 and 3 are a side elevation and a top plan view, respectively, ofa double hand of the present invention. Referring to FIGS. 2 and 3, thedouble hand comprises paired stationary hand unit 2 and pressing handunit 3 constituting the double hand, a pair of fingers 2-1 and 2-2 ofthe stationary hand unit 2, a plate member 2-3 of a pressing unit, apair of fingers 3-1 and 3-2 of the pressing hand unit 3, gripping tips(claws) 2-4, 2-5, 3-4 and 3-5, and a plate member 3-3 of the pressingunit. Reference numbers 4 and 5 designate a pressing mechanism and ahand fitting lug attached to the stationary hand unit 2, respectively.The hand units 2 and 3 have flat gripping surfaces which are orientedperpendicularly to the gripping center axis P of the fingers, aredisposed in parallel along the gripping center axis P with apredetermined distance between them, and are interlinked by the pressingmechanism 4. In the drawing, a symbol W designates a workpiece.

FIG. 4 is a side elevation of the plate members 2-3 and 3-3 of thepressing unit. Each plate member is provided with an opening 6 coaxialwith the gripping center axis P for allowing a workpiece to penetratethrough the plate member, thus each plate member is formed as anintegrated member consisting of a base section 7, connecting sections 8and 9, and a front end section 10. At the central part of the front endsection 10 and near the horizontal edges of the base section 7, fittingholes 11 and, 12 and 13, respectively, for fitting the pressingmechanism are formed.

FIG. 5 illustrates the constitution of three pressing mechanisms 4disposed between the stationary hand unit 2 and the pressing hand unit 3of FIG. 2.

A taper head 51 is fixed to the plate member 3-3 of the pressing unit 3with bolts 52, while a head 53 is fixed to the plate member 2-3 of thestationary hand unit 2 with bolts 54. The upper end of a taper-head rod55 inserted through and from below the taper head 51 is fixed to thehead 53 with a bolt 56. A helical spring 57 is provided between thetaper head 51 and the head 53 coaxially with the taper-head rod 55. Thusthe plate member 3-3 of the pressing hand unit is stably positioned withthe taper part of the taper-head rod 55 firmly fitted in the taper holeof the taper head 51 by the action of the spring 57. When a pressingforce is applied to the pressing plate member 3-3 toward the platemember 2-3, the taper head 51 is raised against the force of the spring57 so that the taper fitting is loosened and the pressing plate member3-3 is released free relative to the stationary plate member 2-3.

FIG. 6 illustrates the driving mechanism of the stationary hand unit 2.The driving mechanism of the pressing hand unit is identical inconstruction with that of the stationary hand unit.

Referring to FIG. 6, the driving mechanism comprises an electromagneticvlave 61, an air cylinder mechanism 62, guide rods 63 and 64, a link 65,a pivot shaft 66, limit switches 67 and 68, a dog 69, and the respectivebosses 70 and 71 of the fingers.

The fingers of the stationary hand 2 are in a fully open state in FIG.6, in which the dog 69 actuates the limit switch 67, thus confirming thefully open state of the fingers. When the piston rod of the air cylindermechanism 62 is pushed out by changing-over the electromagnetic valve61, the boss 71 of the finger 2-1 connected to the piston rod is movedrightward and the link 65 is turned on the pivot shaft 66 so that theboss 70 of the finger 2-1 is moved leftward along the guide rod 63, thusthe fingers 2-1 and 2-3 are moved toward the respective fully closedpositions. The limit switch 68 detects the fully closed state. When theelectromagnetic valve is changed-over to the opposite position, thosecomponent of the mechanism are moved in the opposite directions so thatthe fingers 2-1 and 2-2 return to the respective positions as shown inFIG. 6.

It is obvious from what has been described hereinbefore that the doublehand according to the present invention is capable of gripping aworkpiece, placing the workpiece on a table with the center axis of theworkpiece directed vertically, and then moving freely with respect tothe workpiece along the center axis of the workpiece (the grippingcenter axis) even when the two hand units are disposed in parallel alongthe gripping center axis, since openings for allowing a workpiece topenetrate through the plate members of the pressing unit are providedfor the plate members. Therefore, the change of workpiece grippingposition can simply and easily be attained through the vertical movementof the hand, which is advantageous for the change of workpiece grippingposition. Furthermore, since the base section, front end section, andthe connecting sections of the plate member are integrated into a singlepiece, each plate member is sufficiently rigid and will not adverselyeffect the function of the pressing mechanism.

We claim:
 1. A double hand for an industrial robot, comprising astationary and a pressing hand unit, each hand unit comprising at leasta pair of fingers and a plate member disposed between said hand units,said plate members being disposed in parallel with said fingers of saidcorresponding hand unit along the gripping center axis of said fingers,said pressing hand unit being flexibly connected to said stationary handunit such that the respective gripping center axis of said two handunits are in alignment, said plate members of said pressing hand unitand stationary hand unit being disposed opposite to each other and theopening sides of the respective pairs of fingers of said stationary andpressing hand units being directed in opposite directions, wherein anopening is provided in each of said plate members to allow the workpieceto pass through said plate members coaxially with the respectivegripping center axis of both said hand units.
 2. A double hand, as setforth in claim 1, wherein each of said plate members comprises a basesection, a front end section and two connecting sections which areintegrated into a single piece surrounding said opening for allowing aworkpiece to penetrate through said plate members.